Surface antigens of human prostatic adenocarcinoma will be investigated by human monoclonal antibodies. For the human hybridomas, peripheral blood lymphocytes of prostatic cancer patients who present evidence of immunity to prostatic epithelial cells will be re-stimulated in vitro with prostatic cancer tissues. These cells will be fused with proper human myeloma cells. Hybrid cells will be first screened for their human Ig production. The Ig-producing hybrids will be next screened for their binding specificities to various human cell cultures and be characterized fully for their specificities to normal and malignant prostatic tissues by immunohistological techniques. The surface antigens of prostatic cancer cells will be also investigated by radiolabelling cell surface antigens and immunoprecipitating with monoclonal antibodies, and further the target antigenic determinants will be identified and characterized for their molecular weight, and peptide structures. With the use of monoclonal antibodies of known specificities and clinical specimens, expression of developmental or tumor marker antigens will be investigated to define the clinical relevance of these marker antigens in human prostatic carcinoma.